The present invention relates to a mechanical system for self-destruction of a munition provided with a warhead initiated by a pyrotechnic sequence, in particular a submunition dispersible by a vehicle such as a carrier shell.
The pyrotechnic sequence could comprise a main striker and a priming device composed of a slide movable from a safety position to an armed position and a means for priming the charge.
The self-destruct system comprises a secondary striker (or self-destruct striker) movable within a slide receptacle and designed to strike the primer means. It also comprises a device for activating the displacement of the secondary striker in the direction of the primer means after a preset delay.
In general, after a submunition has been ejected from a vehicle, the slide which carries the charge primer means enters the armed position. When the submunition comes in contact with the ground or a target, the main striker triggers the warhead by striking the primer means.
However, if the pyrotechnic charge should malfunction, the munition will not explode when it contacts the ground or a target. Nonetheless, once stable on the ground, the munition remains dangerous since any new impact could reset the pyrotechnic sequence function and cause the munition to explode.
To remedy this malfunction in the prior art, a submunition, carried in a carrier shell, is provided with a self-destruct system which causes the warhead to explode after a preset delay. This preset delay is greater than the free-fall flight time of the munition which ends when the munition reaches the ground or a target moving on the ground.
U.S. Pat. No. 4,873,927 describes a self-destruct system comprising a pyrotechnic delay which is initiated when the primer-carrying slide is armed. After certain burn-up time of the pyrotechnic sequence, priming of the warhead is initiated. Such a system has the drawback of being very cumbersome.
U.S. Pat. No. 4,998,476 describes a self-destruct system comprising a hydraulic or pneumatic piston. This piston abuts an oil chamber and moves when the volume of this chamber decreases upon opening of a calibrated orifice out of which the oil may flow when the slide enters the armed position. The piston is then displaced and at the end of its travel, it releases a striker which initiates the primer means of the warhead. Such a system is actually a micromechanism that requires high precision in design, assembly, and operation. Hence, it is highly sensitive to the outside environment and is expensive to build.
European Patent EP 0 205 956 describes a self-destruct system having a piston equipped with a secondary striker held by a pin. After ejection of the submunition and passage of the slide into the armed position, the pin gradually yields and breaks under the action of a spring after a given time interval. Such a system has the drawback of not being precise, since the delay is governed by the time the pin takes to fail, which is difficult to control.
British Patent GB 585,026 describes a delayed-action firing system for use with bombs. This system comprises an envelope filled with a solvent. The envelope is pierced when the bomb strikes a target resulting in solvent contacting a fusible washer. When the washer is dissolved, it releases a striker which is urged by a spring and initiates a primer. This system is relatively cumbersome and is difficult to build into a submunition dispersible by a vehicle, particularly in a "bomblet" dispersible by an artillery carrier shell. Also, this system is unreliable because it depends on impacting a target in a very specific direction.
U.S. Pat. No. 2,314,678 describes a self-destruct device for a bomb which has an acid reservoir broken by a hammer when a parachute opens. The acid then spreads in the device and corrodes a striker holding ring. This device is also very cumbersome. Moreover, it can only function in the vertical position because the acid depends on gravity to contact the ring.
German Patent DE 116,726 describes a device for initiating a primer after a delay. This device combines a sponge designed to receive a solvent and a soluble washer which holds a striker. Such a device requires "manual" placement of the solvent which cannot be adapted for self-destruction of a munition or submunition.
German Patent DE 353 87 87 describes a self-destruct system for a dispersible anti-tank submunition. This system has an ampule containing an acid designed to corrode the stem of the main striker. The acid ampule is broken when the striker is withdrawn. This occurs during the trajectory of the submunition and after the nut attached to the striker is unscrewed. The efficiency of this system is debatable because it is difficult to see how the striker could re-strike the primer to allow self-destruction.
U.S. Pat. No. 3,559,580 describes a timer for neutralizing an undersea mine. A battery supplies current to a system that contains an anode soluble in an electrolyte. When the anode is totally dissolved, it causes a valve to open allowing seawater to flow into the mine, which has the effect of neutralizing it. Such a device cannot easily be used to neutralize or destroy a munition, particularly a dispersible submunition. Moreover, it requires a substantial energy source.